Treatment of food materials



. Dec. 20, 1938. w. w. COWGILL 2,140,788

TREATMENT OF FOOD MATERIALS Filed June 12, 1937 ill Patented Dec. 2c, 1938 PATENT OFFICE -TREATM'.ENT OF FOOD MATERIALS William W. Cowgill, Fairfield, Conn, assignor to Sardik Incorporated, Jersey City, N. .L, a corporation of Delaware Application June 12, 1937, Serial No. 147,893

12 Claims.

This invention relates to the treatment of food materials to render them resistant to deterioration by reducing their moisture content to a predetermined point.

An object of this invention is to provide an improved method of drying food materials, of such character as to permit an accurate control of the drying period and the definite termination of the drying operation at that instant when the desired degree of drying has been reached, thus eliminating the hazard of injuring the fresh material by too prolonged heating or overheating thereof.

A further object is to provide a method of drying food materials on a drying surface, in which the bad efiects caused by residual heat held in the material at the end of the drying operation are eliminated.

These and other objects which will be apparent to those skilled in this particular art are attained by the present invention, one embodiment of which is hereinafter set forth by way of illustration.

The present invention relates particularly to methods of treating food materials in which the fresh material is dispersed over a suitable drying surface, subjected to a drying operation while on said surface, and then removed from the surface when the moisture content has been reduced to substantially the desired point. Heat is usually employed in producingthe desired evaporation of moisture from the material, preferably by heating the drying surface. As long as there is sufiicient moisture in the material being dried to provide a relatively strong ebullition the material is, of course, protected against overheating due to the latent heat of vaporization taken up by the evaporating moisture. However, as soon as the material reaches a relatively lowrmois ture content and the larger part, of the moisture has been. evaporated therefrom there isno longer such an active ebullition as will suitably protect the material and the temperature thereof is liable to rise rapidly and to an unsafe degree at this point. Heretofore, in conventional drying operations,

' overheating has usually occurred at this point.-

At the same time, even though the material is promptly removed from the. drying surface, the

residual heat in the dry material has the effect of continuing the drying operation beyond the point desired. 3

Although the drying of food material while distributed over drying surfaces may be accomplished on various types of surfaces it is usually done at the present time'on rotary drums which are interiorly heated by steam. The drums rotate continuously, the fresh material is fed to and dispersed across the surface of the drum as it rotates and is dried thereon while it adheres to and moves with such surface. The dried material is continuously removed from the rotating 5 drum by a suitable doctor or scraper mechanism such, for example, as a knife blade extending across and pressed against the face of the drum. Theoretically, the material is scraped from the drum surface as soon as the moisture content has been reduced to the desired point, but heretofore the heating effect has usually been prolonged beyond the instant of removal both because of residual heat in the dry material and because the scraper mechanism reaches substantially the 3 temperature of the drying surface with which it is in close contact, and thus continues the heating efiect upon the-material which tends to remain in contact with such mechanism even after it has been separated from the drum surface, particularly when the material is removed while in a tacky condition which increases its tendency to adhere to the hot scraper mechanism.

In the present invention this hazard is eliminated by insuring that the material is not only separated from the drum surface at the proper point, but that it is prevented from remaining in contact with the scraper or knife for any length of time thereafter and is definitely removed from such contact substantially immediately upon its separation from the drum surface.

- In many surface drying operations the dry material is separated from the drying surface in the form of a substantially'continuous film or sheet. Under such circumstances, the results of the present invention can be attained by subjecting such film or sheet to a continuously applied tension'which has the effect of pulling the material off and away from the scraper mechanism or knife as soon as the latter has freed the material 40 from the drying surface, and so overcoming any tendency ofthe material to adhere to the scraper and become overheated thereon. a

It will be apparent that this operation requires a finished product having sufficient tensile strength to permit its being pulled away from the scraper mechanism without causing the film or sheet to disintegrate. Some materials and the products of some drying operations have this necessary characteristic, but other materials and Q the products of other processes require special treatment. V I

Those materials which in dry film form. would not have suflicient tensile strength, as well as those which tend to form a powder rather than a continuous film upon removal from the drying surface, are so treated as to permit removal in film form having the required strength characteristics.

For example, a suitable binding material capable of insuring the necessary strength in the finished film can be incorporated in the food material prior to its being dispersed over the drying surface. The binder is preferably such as to impart no undesirable qualities to the finished product and in certain circumstances may be of such character as to impart qualities which are desired in the finished product but would not otherwise be Dresent.

v The drawing illustrates diagrammatically one arrangement of apparatus which'is satisfactory for carrying out the present invention. It comprises a drying drum ID on which the material to I be dried is dispersed from a suitable feeding mechanism such as a distributor head formed by a feed tube ll, having perforations l2 along the bottom, and extending across the top of the drum adjacent a distributor roll I3 which insures the proper distribution of the material over the drum surface. The material to be dried is delivered in pulp form to the feed tube Ii from any suitable source of supply. A scraper mechanism which includes a knife blade l4 removes the finished material from the drum in the form of a substantially continuous film l5 and this film is subjected to tension for the purpose of pulling it away from the knife blade substantially instantaneously upon its separation from the drying surface.

Any type of mechanism for applying tension to the film can be employed. That shown in the drawing consists of a pair oftake-oil? rolls l6 and I! which engage opposite faces of the film and rotate at such a speed as. to apply sufficient, tension to the film to draw it away from the knife blade substantially instantaneously with its separation from the drum surface, without, however, injuring or breaking the film.

Immediately adjacent-the scraper mechanism is a cooling zonethrough which the film is drawn by the take-off rolls to extract residual heat from the film as soon as it is drawn away from the scraper. The cooling zone is indicated diagrammatically in the drawing by a cooling chamber l8 in which the take-off rolls are located. This zone cooperates with the take-off rolls in preventing overheating of the film as a result either of residual heat in the film'or. of too prolonged contact with the scraper mechanism after separation from thewdrying surface. The dry and cool film can be collected in any desired manner as, for example, by. delivering it to a rotating worm l9 which breaks it up and conveys it to a packing station.

Some fruits and vegetables, such, for example, as cranberries, either naturally contain suificient binding substance to adapt them to the present process, or can beitreated to increase or improve the binding substance naturally present for that purpose.- In other cases, particularly when it is desired to dry substantially clear fruit juices, or

. traneous binding substance to the material being similar materials, it is necessary to add an-exdried, and this is preferably done before thedrying operationis commenced.

The binding substance may be provided by such I vegetable gums as, for example, pectin, agar-agar,

gum tragacanth, gum arabic, or acacia; it may be a suitable coagulated or gelatinized starch such,

for example, as arrow root, casava, corn starch,

rice starch, wheat starch, or sago; or it may be some material containing a sumcient quantity of such a gum or starch. When treating lemon or orange juice,'I have found corn syrup or invert sugar satisfactory.

When an extraneous binder is added to a material to be dried, the amount added will depend somewhat upon the amount of the above binding substance. or substances which may be naturally present in the original material. In the case of pectin, for example, approximately 1% to 3% by weight will be sufiicient to produce the necessary binding efiect in the dry film, and substantially the same proportions of any of the above starches, suitably gelatinized, will be sufficient. With such materials as tomato, for example, approximately 1 of the binder will be sufilcient, while in treating prunes and similar materials approximately 3% will be required.

The starches are gelatinized by a gradual heat treatment. For example, casava starch is usually prepared by heating in water at approximately 70 to 80 C. for about 5 minutes at which point it will have substantially its greatest swelling capacity and thus the greatest viscosity will be obtained. r

Cranberries are typical of those materials which can be treated so as to provide a sufficient percentage of pectin from the natural ingredients present to eliminate any need for adding an extraneous binder in order to obtain a dry product havin the required tensile strength. .With materials of this sort the natural pectin present is released by converting the protopectin in the original berries into pectin. This is done by heating the fruit with asmall amount of water for a short period of time. The pectin as it is liberated becomes hydrated by contact with the water and swellsinto a gelatinous mass. Due to the relatively small amount of water employed the larger part of the pectin remains undissolved, and since the hydrolytic action on the undissolved pectinis much less than on the dissolved pectin, the result of the operation is to provide in the fruit or vegetable pulp a pectin of high jelly grade. This becomes important when the fin- The cranberries are first washed thoroughly I and are then cooked in the presence'of extraneous water which is added to assist in the release of pectin. The cooking is preferably done in a steam jacketed kettle and the ratio of water to berries is approximately 1 to 3.5, although it may be varied from 1 to 2, to 1 to 4.5 with good results. The cooking temperature is preferably about boiling. In some cases the natural material may be crushed-or cut up and cooked without the addition of water.

The purpose of the cooking or boiling operation is to. convert as muchas P ssible of'the protopectin'content of the original material into pectin and at the same time minimize the destructive efiect of heat upon the pectin itself so that it will not only be an effective binder but will Preferably, the operation is so controlled as to produce pectin having the highest possible number of jelly units, the number of which is obtained by multiplying the pectin yield by the grade of pectin produced. Too short a cooking period produces an insuflicient yield of pectin to accomplish the desired results, while too long a cooking period results in too low a grade of pectin, the prolonged heating having a destructive effect upon the jelly grade of the pectin obtained. The boiling operation is preferably conducted so as to produce in the material pectin having a jelly grade of not less than 250 and a yield sufilcient to produce not less than sixtyseven jelly units per pound. It is, of course, well known that a pectin having a jelly grade of 250, means a pectin capable of jellying 250 times its own weight of sugar.

During the cooking operation the material is subjected to a vigorous agitation in order to mechanically separate the cellular particles from each other and to free the pectin which is found on andbetween the cell walls. The berries are boiled for approximately five minutes, the time of boiling depending somewhat upon the degree of ripeness. The riper the berry the shorter the time of boiling.

As soon as the boiling operation is terminated the material is rapidly run through a pulper filled with an inert atmosphere for protection against oxidation and containing a fine screen or sieve to remove the seeds and skins and to break up the gelatinous pectin binding material. Preferably the screen comprises a mesh of about .024, al though larger meshes may be preferred with some products. The resulting pulp is then run into a tank where it is subjected to a vigorous mechanical agitation in order to homogenize the material and to distribute the pectin binder homogeneously throughout the entire mass. As soon as possible after the boiling operation the pulp is cooled to 40 C. or below, to prevent injury to the pectin by the heat, whereupon it is ready to be dried on the drying drum.

On the other hand, strained fruit juices are examples of material which requires the addition of an extraneous binding substance thereto prior to drying, and this can be provided either by adding a liquid dispersion of pectin, for example, to the juice, or by adding a dry pectin directly to the fruit juices and dispersing it therein. A coagulated starch can, as pointed out above, be employed in place of pectin if desired. However, wher the dry fruit juice is to be used ultimately for the manufacture of jelly it will be more satisfactory to use pectin as the binding substance rather than a coagulated starch as pectin is a necessary ingredient in jelly making. In such circumstances more pectin will be added to the original material than would be needed merely for binding purposes under the present invention.

If the product is not to be employed in jelly mak-.

ing, from 1% .to 3% pectin or coagulated starch will constitute a sufficient binder, but if the material is to be used in jelly making it will require about 4% to 6% pectin, depending upon the amount and grade of pectin already present in the fruit;

In carrying out the present invention, the ma- I terial to be dried having the proper amount. of

continuous sheet or film by the knife blade H. The drying operation is so controlled that the scraper or knife separates the finished material fifteen seconds on a surface heated to about.

125 C. to reduce the moisture content to about 1 In drying strained fruit juices the material is dried for about ten to fifteen seconds on a surface heated to about 129 C. to reduce the moisture content to approximately 1.5% to 4%, or any other desired amount. Lemon juice, for example, can be dried in about ten seconds on a surface heated to about 129 0., while orange juice may require about twelve seconds and other juices about fifteen seconds. Obviously, the time and temperature of treating any material can be varied within relatively wide limits to produce various percentages of moisture in the finished material.

From the knife the film passes between the takeoif rolls, which pull the material away from the knife blade as soon .as it is separated from the drying surface and through the cooling zone, thus preventing overheating due to prolonged contact with the heated knife blade and also causing residual heat to be extracted from the film during passagethrough the cooling zone.

The result is a dry food material having the desired reduced moisture content but which has been protected against the bad effects of too prolonged or overheating. When pectin in jelly making. proportions has been added the dry ma terial can be used in making jelly by adding it to a standard sugar solution and acid, and properly mixing.

It will be apparent that the invention can be variously modified and adapted within the scope of the appended claims.

I claim:

1. The improvement in the art of preparing a concentrated food product of reduced moisture content while preventing overheating thereof,.

with sufficient tensile strength to permit said I film being placed under tension without break ing, and continuously pulling said film away from said surface under tension as the material is separated therefrom.

2. The improvement in the art of preparing a concentrated food product, of reduced moisture content while preventing overheating thereof,

which comprises spreading over a drying surface.

fresh material having incorporated. therein a. binding agentcapable of giving tensile strength to the material after drying, subjecting the material on said surface to a drying temperature to "reduce the moisture contentthe'reof to a predetermined' point, then progressively separating the material from said surface in the form of a substantially continuous film having said binding agent incorporated therein to provide said film with suflicient tensile strength to permit said content while preventing overheating thereof,

which comprises spreading over a heated drying surface fresh material having pectin incorporated therein in an amount sufiicient to give tensile strength to the material after drying, subjecting the material on said surface to a drying temperatureto reduce the moisture content thereof to a predetermined point, then progressively separating the material from said surface in the form of a substantially continuous film having said pectin incorporated therein to provide said film with suflicient tensile strength to permit said film being placed under tension without breaking, and continuously pulling said film away from said surface under tension as rapidly as the material is separated therefrom. a

. 4. The improvement in the art of preparing a concentrated food product of reduced moisture content while preventing overheating thereof.

which comprises spreading over a heated drying surface fresh material having gelatinized starch incorporated therein in an amount sufiicient to give tensile strength to the material after drying, subjecting the material on said surface to a drying temperature to reduce the moisture content thereof to a predeterminedpoint, then instantly and progressively separating the material from said surface in the form of a substantially continuous. film having saidst'arch incorporated therein to provide said film with sufilcient tensile strength to permit said film being placed under tension without breaking, and continuously p'ulling said film away from said surface under tension as rapidly as the material is separated therefrom. r

5L The improvement in the art of preparing a concentrated food product of reduced moisture content, which comprises convertingthe protopectin content of a natural material into pectin capable of giving tensile strength to the finished material. forming a pulp of the material and agitating it to distribute the pectin binder uniformly throughout the mass,- then distributing the pulp with the pectin incorporated therein over a drying surface, subjecting the material on said surface to a drying temperature to reduce the moisture content thereof to a predetermined point, then progressively separating the material from said surface in the form of a substantially continuous film having said pectin incorporated therein and providing said film with sumcient tensile strength to permit said film being placed under tension without breaking, and continuously pulling saidfilm away from said }surface under tension as rapidly as the material is separated therefrom. V "i 6. The improvement in the art of preparing a concentrated food product of reduced moisture content containing pectin in grade and quantity suitable for jelly making upon the addition of sugar' and water, which comprises converting the protopectin content of a natural material into pectin of the desired grade and quantity,

pulping the material and agitating it to dis tribute the pectin uniformly throughout the mass, then distributing the pulp with, the pectin in corporated therein over a dryings'urface, subjectingthematerial on said surface to a drying concentrated food product of reduced moisture] content from fruit juice while preventing overheating thereof, which comprises incorporating pectin in the original juice in an amount sumcient to givetensile strength to the material after drying, then distributing said juice having the pectin incorporatedtherein over a heated.-

drying surface, subjecting the material on said surface to a drying temperature to reduce the moisture content thereof to a predetermined point, then progressively separating the material from said surface in the form of a substantially continuous film having said pectin incorporated therein to provide said film with sufilcient tensile strength to permit said film being placed under tension without'breaking', and continuously 'pu1iing said film away from said surface under tension as rapidly as the material is separated therefrom.

8. The improvement in the art of preparing a concentrated food product of reduced moisture content from fruit juice while preventing overheating thereof, which comprises incorporating a gelatinized starch inthe original juice in an amount sumcient to give tensile strength to the material after dryin g,spreading said juice having the gelatinized starch incorporated therein over a heated drying surface, subjecting the material on said surface to a drying temperature to reduce the moisture content thereof to a predetermined point, then progressively separating the material from said surface in the form of a substantially continuous film having said starch incorporated therein to provide said film with sufilcient tensile strength to permit said film being placed under tension without breaking, and continuously pulling saidfilm away fromsaid surface under tension as rapidly as the material is separated therefrom.

9. The improvement in the art of preparing a concentrated food product of reduced moisture content which comprises spreading over a heated drying surface fresh material having incorporated therein a binding agent capable of giving tensile strength to the material after drying, subjectin'g the material on said surface for approximately 15 seconds to a temperature of approximately 125 C. to reduce the moisture content thereof to a predetermined point, thenprogressively separating the material from said surface in the form of asubstantially continuous film having said binding agent incorporated therein to provide said film with suflicient tensile strength to permit said film being placed under tension without breaking, and continuously pull ing said film away from said surface under tension'a's the material is separated therefrom;

10. The improvement in the art of preparing a concentrated food product of reduced moisture content from fruit juices while preventing overheating thereof, which comprises incorporating a binding agent in the original juice in an amount sufiicient to give tensile strength to the material after drying, then distributing said juice. having .-the binding agent incorporated therein over a heated drying surface, subjecting the material seconds to a drying temperature of approximately 129 C. to reduce the moisture content thereof to a predetermined point, then progressively separating the material from said surface in the form of a substantially continuous film having said binding agent incorporated therein to provide said film with sufiicient-tensile strength to permit said film being placed under tension without breaking, and continuously pulling said film away from said surface under tension as the material is separated therefrom.

11. The improvement in the art of preparing a concentrated food product of reduced moisture content while preventing overheating thereof,

which comprises spreading fresh material over a;

- drying surface, subjecting the material on said 20 point, then progressively separating the material from said surface in the form of a substantially continuous film, and applying tension to said film so as to continuously pull said film away from said surface as rapidly as the material is separated therefrom.

12. The improvement in the art of preparing a concentrated food product of reduced moisture content while preventing overheating thereof, which comprises spreading fresh material over a drying surface, subjecting the material on said surface to a drying temperature to reduce the moisture content thereof to a predetermined point, then progressively separating the material from said surface in the form of a substantially continuous film; and applying tension to said film so as to continuously pull said film away from said surface and into a cooling zone as rapidly as the material is separated from said surface.

WILLIAM W. COWGILL. 

